diff --git a/run-build.sh b/run-build.sh
index e931776..da571a7 100755
--- a/run-build.sh
+++ b/run-build.sh
@@ -48,6 +48,7 @@
 cd mbedtls
 git apply ../trusted-firmware-m/lib/ext/mbedcrypto/*.patch
 
+rm -rf ../trusted-firmware-m/build
 mkdir ../trusted-firmware-m/build
 cd ../trusted-firmware-m/build